/*
 * @(#)StringContent.java	1.37 00/02/02
 *
 * Copyright 1997-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */
package javax.swing.text;

import java.util.Vector;
import java.io.Serializable;
import javax.swing.undo.*;
import javax.swing.SwingUtilities;

/**
 * An implementation of the AbstractDocument.Content interface that is 
 * a brute force implementation that is useful for relatively small 
 * documents and/or debugging.  It manages the character content
 * as a simple character array.  It is also quite inefficient.  
 * <p>
 * It is generally recommended that the gap buffer or piece table 
 * implementations be used instead.  This buffer does not scale up
 * to large sizes.
 * <p>
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with 
 * future Swing releases.  The current serialization support is appropriate
 * for short term storage or RMI between applications running the same
 * version of Swing.  A future release of Swing will provide support for
 * long term persistence.
 *
 * @author  Timothy Prinzing
 * @version 1.37 02/02/00
 */
public final class StringContent implements AbstractDocument.Content, Serializable {

    /**
     * Creates a new StringContent object.  Initial size defaults to 10.
     */
    public StringContent() {
	this(10);
    }

    /**
     * Creates a new StringContent object, with the initial
     * size specified.  If the length is < 1, a size of 1 is used.
     *
     * @param initialLength the initial size
     */
    public StringContent(int initialLength) {
	if (initialLength < 1) {
	    initialLength = 1;
	}
	data = new char[initialLength];
	data[0] = '\n';
	count = 1;
    }

    /**
     * Returns the length of the content.
     *
     * @return the length >= 1
     * @see AbstractDocument.Content#length
     */
    public int length() {
	return count;
    }

    /**
     * Inserts a string into the content.
     *
     * @param where the starting position >= 0 && < length()
     * @param str the non-null string to insert
     * @return an UndoableEdit object for undoing
     * @exception BadLocationException if the specified position is invalid
     * @see AbstractDocument.Content#insertString
     */
    public UndoableEdit insertString(int where, String str) throws BadLocationException {
	if (where >= count) {
	    throw new BadLocationException("Invalid location", count);
	}
	char[] chars = str.toCharArray();
	replace(where, 0, chars, 0, chars.length);
	if (marks != null) {
	    updateMarksForInsert(where, str.length());
	}
	return new InsertUndo(where, str.length());
    }

    /**
     * Removes part of the content.  where + nitems must be < length().
     *
     * @param where the starting position >= 0
     * @param nitems the number of characters to remove >= 0
     * @return an UndoableEdit object for undoing
     * @exception BadLocationException if the specified position is invalid
     * @see AbstractDocument.Content#remove
     */
    public UndoableEdit remove(int where, int nitems) throws BadLocationException {
	if (where + nitems >= count) {
	    throw new BadLocationException("Invalid range", count);
	}
	String removedString = getString(where, nitems);
	UndoableEdit edit = new RemoveUndo(where, removedString);
	replace(where, nitems, empty, 0, 0);
	if (marks != null) {
	    updateMarksForRemove(where, nitems);
	}
	return edit;
	
    }

    /**
     * Retrieves a portion of the content.  where + len must be <= length().
     *
     * @param where the starting position >= 0
     * @param len the length to retrieve >= 0
     * @return a string representing the content; may be empty
     * @exception BadLocationException if the specified position is invalid
     * @see AbstractDocument.Content#getString
     */
    public String getString(int where, int len) throws BadLocationException {
	if (where + len > count) {
	    throw new BadLocationException("Invalid range", count);
	}
	return new String(data, where, len);
    }

    /**
     * Retrieves a portion of the content.  where + len must be <= length()
     *
     * @param where the starting position >= 0
     * @param len the number of characters to retrieve >= 0
     * @param chars the Segment object to return the characters in
     * @exception BadLocationException if the specified position is invalid
     * @see AbstractDocument.Content#getChars
     */
    public void getChars(int where, int len, Segment chars) throws BadLocationException {
	if (where + len > count) {
	    throw new BadLocationException("Invalid location", count);
	}
	chars.array = data;
	chars.offset = where;
	chars.count = len;
    }

    /**
     * Creates a position within the content that will
     * track change as the content is mutated.
     *
     * @param offset the offset to create a position for >= 0
     * @return the position
     * @exception BadLocationException if the specified position is invalid
     */
    public Position createPosition(int offset) throws BadLocationException {
	// some small documents won't have any sticky positions
	// at all, so the buffer is created lazily.
	if (marks == null) {
	    marks = new Vector();
	}
	return new StickyPosition(offset);
    }

    // --- local methods ---------------------------------------

    /**
     * Replaces some of the characters in the array
     * @param offset  offset into the array to start the replace
     * @param length  number of characters to remove
     * @param replArray replacement array
     * @param replOffset offset into the replacement array
     * @param replLength number of character to use from the
     *   replacement array.
     */
    void replace(int offset, int length, 
		 char[] replArray, int replOffset, int replLength) {
	int delta = replLength - length;
	int src = offset + length;
	int nmove = count - src;
	int dest = src + delta;
	if ((count + delta) >= data.length) {
	    // need to grow the array
	    int newLength = Math.max(2*data.length, count + delta);
	    char[] newData = new char[newLength];
	    System.arraycopy(data, 0, newData, 0, offset);
	    System.arraycopy(replArray, replOffset, newData, offset, replLength);
	    System.arraycopy(data, src, newData, dest, nmove);
	    data = newData;
	} else {
	    // patch the existing array
	    System.arraycopy(data, src, data, dest, nmove);
	    System.arraycopy(replArray, replOffset, data, offset, replLength);
	}
	count = count + delta;
    }

    void resize(int ncount) {
	char[] ndata = new char[ncount];
	System.arraycopy(data, 0, ndata, 0, Math.min(ncount, count));
	data = ndata;
    }

    synchronized void updateMarksForInsert(int offset, int length) {
	if (offset == 0) {
	    // zero is a special case where we update only
	    // marks after it.
	    offset = 1;
	}
	int n = marks.size();
	for (int i = 0; i < n; i++) {
	    PosRec mark = (PosRec) marks.elementAt(i);
	    if (mark.unused) {
		// this record is no longer used, get rid of it
		marks.removeElementAt(i);
		i -= 1;
		n -= 1;
	    } else if (mark.offset >= offset) {
		mark.offset += length;
	    }
	}
    }

    synchronized void updateMarksForRemove(int offset, int length) {
	int n = marks.size();
	for (int i = 0; i < n; i++) {
	    PosRec mark = (PosRec) marks.elementAt(i);
	    if (mark.unused) {
		// this record is no longer used, get rid of it
		marks.removeElementAt(i);
		i -= 1;
		n -= 1;
	    } else if (mark.offset >= (offset + length)) {
		mark.offset -= length;
	    } else if (mark.offset >= offset) {
		mark.offset = offset;
	    }
	}
    }

    /**
     * Returns a Vector containing instances of UndoPosRef for the
     * Positions in the range
     * <code>offset</code> to <code>offset</code> + <code>length</code>.
     * If <code>v</code> is not null the matching Positions are placed in
     * there. The vector with the resulting Positions are returned.
     *
     * @param v the Vector to use, with a new one created on null
     * @param offset the starting offset >= 0
     * @param length the length >= 0
     * @return the set of instances
     */
    protected Vector getPositionsInRange(Vector v, int offset,
						      int length) {
	int n = marks.size();
	int end = offset + length;
	Vector placeIn = (v == null) ? new Vector() : v;
	for (int i = 0; i < n; i++) {
	    PosRec mark = (PosRec) marks.elementAt(i);
	    if (mark.unused) {
		// this record is no longer used, get rid of it
		marks.removeElementAt(i);
		i -= 1;
		n -= 1;
	    } else if(mark.offset >= offset && mark.offset <= end)
		placeIn.addElement(new UndoPosRef(mark));
	}
	return placeIn;
    }

    /**
     * Resets the location for all the UndoPosRef instances
     * in <code>positions</code>.
     *
     * @param positions the positions of the instances
     */
    protected void updateUndoPositions(Vector positions) {
	for(int counter = positions.size() - 1; counter >= 0; counter--) {
	    UndoPosRef ref = (UndoPosRef)positions.elementAt(counter);
	    // Check if the Position is still valid.
	    if(ref.rec.unused) {
		positions.removeElementAt(counter);
	    }
	    else
		ref.resetLocation();
	}
    }

    private static final char[] empty = new char[0];
    private char[] data;
    private int count;
    transient Vector marks;

    /**
     * holds the data for a mark... seperately from
     * the real mark so that the real mark can be 
     * collected if there are no more references to
     * it.... the update table holds only a reference
     * to this grungey thing.
     */
    final class PosRec {

	PosRec(int offset) {
	    this.offset = offset;
	}

	int offset;
	boolean unused;
    }

    /**
     * This really wants to be a weak reference but
     * in 1.1 we don't have a 100% pure solution for
     * this... so this class trys to hack a solution 
     * to causing the marks to be collected.
     */
    final class StickyPosition implements Position {

	StickyPosition(int offset) {
	    rec = new PosRec(offset);
	    marks.addElement(rec);
	}

        public int getOffset() {
	    return rec.offset;
	}

	protected void finalize() throws Throwable {
	    // schedule the record to be removed later
	    // on another thread.
	    rec.unused = true;
	}

        public String toString() {
	    return Integer.toString(getOffset());
	}

	PosRec rec;
    }

    /**
     * Used to hold a reference to a Position that is being reset as the
     * result of removing from the content.
     */
    final class UndoPosRef {
	UndoPosRef(PosRec rec) {
	    this.rec = rec;
	    this.undoLocation = rec.offset;
	}

	/**
	 * Resets the location of the Position to the offset when the
	 * receiver was instantiated.
	 */
	protected void resetLocation() {
	    rec.offset = undoLocation;
	}

	/** Location to reset to when resetLocatino is invoked. */
	protected int undoLocation;
	/** Position to reset offset. */
	protected PosRec rec;
    }

    /**
     * UnoableEdit created for inserts.
     */
    class InsertUndo extends AbstractUndoableEdit {
	protected InsertUndo(int offset, int length) {
	    super();
	    this.offset = offset;
	    this.length = length;
	}

	public void undo() throws CannotUndoException {
	    super.undo();
	    try {
		synchronized(StringContent.this) {
		    // Get the Positions in the range being removed.
		    if(marks != null)
			posRefs = getPositionsInRange(null, offset, length);
		    string = getString(offset, length);
		    remove(offset, length);
		}
	    } catch (BadLocationException bl) {
	      throw new CannotUndoException();
	    }
	}

	public void redo() throws CannotRedoException {
	    super.redo();
	    try {
		synchronized(StringContent.this) {
		    insertString(offset, string);
		    string = null;
		    // Update the Positions that were in the range removed.
		    if(posRefs != null) {
			updateUndoPositions(posRefs);
			posRefs = null;
		    }
	      }
	    } catch (BadLocationException bl) {
	      throw new CannotRedoException();
	    }
	}

	// Where the string goes.
	protected int offset;
	// Length of the string.
	protected int length;
	// The string that was inserted. To cut down on space needed this
	// will only be valid after an undo.
	protected String string;
	// An array of instances of UndoPosRef for the Positions in the
	// range that was removed, valid after undo.
	protected Vector posRefs;
    }


    /**
     * UndoableEdit created for removes.
     */
    class RemoveUndo extends AbstractUndoableEdit {
	protected RemoveUndo(int offset, String string) {
	    super();
	    this.offset = offset;
	    this.string = string;
	    this.length = string.length();
	    if(marks != null)
		posRefs = getPositionsInRange(null, offset, length);
	}

	public void undo() throws CannotUndoException {
	    super.undo();
	    try {
		synchronized(StringContent.this) {
		    insertString(offset, string);
		    // Update the Positions that were in the range removed.
		    if(posRefs != null) {
			updateUndoPositions(posRefs);
			posRefs = null;
		    }
		    string = null;
		}
	    } catch (BadLocationException bl) {
	      throw new CannotUndoException();
	    }
	}

	public void redo() throws CannotRedoException {
	    super.redo();
	    try {
		synchronized(StringContent.this) {
		    string = getString(offset, length);
		    // Get the Positions in the range being removed.
		    if(marks != null)
			posRefs = getPositionsInRange(null, offset, length);
		    remove(offset, length);
		}
	    } catch (BadLocationException bl) {
	      throw new CannotRedoException();
	    }
	}

	// Where the string goes.
	protected int offset;
	// Length of the string.
	protected int length;
	// The string that was inserted. This will be null after an undo.
	protected String string;
	// An array of instances of UndoPosRef for the Positions in the
	// range that was removed, valid before undo.
	protected Vector posRefs;
    }
}